Under CopyrightHenschel, HenningHenningHenschelKöhn, OtmarOtmarKöhnSchmidt, Hans UlrichHans UlrichSchmidt2022-03-0825.9.20101992https://publica.fraunhofer.de/handle/publica/32016510.24406/publica-r-32016510.1109/RADECS.1991.213571The proven way of determining induced loss of optical fibres are transmission loss measurements. For longterm irradiations of radiation hard fibres at low dose rates, however, the induced loss is mostly small compared to the unavoidalble drifts of the measuring system. Measurements with OTDRs where each time a new absolute loss measurement is performed could overcome this problem, provided this method yields the same results as transmission loss measurements. We made measurements on single mode and graded index fibres with OTDRs of three different manufacturers and found that, under comparable conditions, OTDR measurements yield exactly the same results.enbackscatter measurementoptical fibresOptical Time Domain ReflectometerOTDRphotobleachingradiation induced losstransmission loss measurement620conference paper